histedit: fix silly bug that was unpacking a bytestr before writing it
I have this foggy notion that popbuffer() might have returned a list
in the past, but it doesn't anymore, and this was breaking on Python
3. As a bonus, it's probably a ton faster on Python 2 now.
Differential Revision: https://phab.mercurial-scm.org/D2243
Our full contribution guidelines are in our wiki, please see:
https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).